Definition of accuracy

[new23d]

Just wondering what the definition of accuracy is in the product spec. Base on what I have read , there are volumetric accuracy and local accuracy for 3D scanners. Which one does the figure in the spec refer to ?

[ivan]

Hi! does this post answers your question enough?

Question about MIRACO

I don’t mixed anything Precision has nothing to do with accuracy If you saw accuracy of 0.02mm it was probably a mistake as people often mix that terms together . Probably webmaster made error . Accuracy and precision are two measures of observational error. Accuracy is how close a given set of measurements are to their true value ( how well the scanned object can be reproduced in their details and volume compared to the original object ) , while precision is how close the measurements are t…

[ivan]

Accuracy refers to single frame, volume accuracy depends on stitching which was good at the beginning (pop1) and only got better over time

here some interesting videos on this subject (for pop 2 and old software)

Revopoint POP2 Single View Accuracy and Precision Tests

Revopoint POP2 3D Scanner Scan Volume and Flatness Error

and here a great tip from @PUTV how to obtain the greatest accuracy over an object, beware the optimal scanning distance for each revopoint scanner and different scanning mode.

Pop 2 Volumetric Accuracy

@jleal7 the accuracy is based on the scanning distance of 15cm to the scanned object . Having scans with different modes will change the accuracy , also different distances will affect that . So scanning in feature mode don’t give you the same accuracy as Body mode . Try to keep the scanning distance at the same levels and at the same modes possible. .

[PUTV]

@new23d

Just wondering what the definition of accuracy is in the product spec. Base on what I have read , there are volumetric accuracy and local accuracy for 3D scanners. Which one does the figure in the spec refer to ?

Hi @new23d

I think @ivan provided you already with the most informative posts .

But to get it easy on the brain :

1. Precision accuracy : the precision between 2 scans and the error between them , you scan 2 scans of the same object expecting them to be accurate at its best …that where the Precision accuracy is about , lower value is better
   The precision accuracy is measured with a single frame capture in lab environment using special for that created measuring tools ( very expensive tools)

2. Volume accuracy : the accuracy between the scanned volume vs the original scanned object , you scan an object expecting the accuracy to be on the higher level , the Scanner accuracy numbers will tell you how much error you can expect between the scanned volume vs the original volume , lower value is better.
   Volume accuracy is measured with a single frame capture in lab environment using special for that created measuring tools ( very expensive tools)

3. Pointcloud Resolution : the resolution is about the 2 point distance of a point cloud , lower value is better

4. Meshing Resolution : the resolution of a meshed pointcloud depends on the value. However if you use higher mesh resolution than your original Pointcloud Resolution you will induce artificial points and that can results in uneven surface or bumpy sandy appearance. Always match your mesh resolution to the resolution of your pointcloud for best results and details …

As normally higher values in meshing deliver better results under 3D modeling , with 3D scanning it is slightly different , because the main focus is to get the proper authentic volume first … after that you can move your mesh to your favorite software and do as you please … remember than any editing and processing on the mesh can decrease the original accuracy…

[PUTV]

Testing accuracy or precision using every day objects is same as eyeballing it . There is so many factors that can alter it , for example the height of the object or length regardless to the angle of the scanner , where the begining of a scanned object can be more accurate on the top vs the bottom … for that reason a special and very expensive tools are used for that type of measurements reflecting the full potential of the hardware .
As usual an error of 0.1 mm is fairly acceptable while scanning , considering a hair wide is around 0.05 to 0.08 mm

Volume error accuracy in size :

10 Microns 0.01mm : grain of polen ( not visible with naked eye
20 Microns 0.02mm : silt ( not visible with naked eye )
50 Microns O.05mm : the edge of a paper sheet
80 Microns 0.08mm : human hair
100 Microns 0.1mm : grain of salt
200 Microns 0.2mm : grain of gravel
The size above can also apply to resolution of the surface .

Next time you purchase a 3D scanner , remember about the error accuracy listed on specifications , but don’t think you going to scan a single hair just because the scanner have 0.05mm accuracy , the accuracy refer to an error in volume while scanning , and not what you can scan with . 3D scanners are not microscope after all . The minimum volume you can scan with a scanner software are always listed in the specifications .

For example Revopoint MINI : you can scan a minum volume of a 10x10x10 mm ( actually 6mm ) object with an error of volume accuracy of 0.02mm between the original volume and scanner volume and accuracy precision of 0.01mm between multiple scans of the same object .

I hope it is much clear now